Ttdfjt

Lieutenant in British English is pronounced with an f: /lɛfˈtɛnənt/.

"Colonel", which is pronounced identically to "kernel", as though the "lo" in the middle was somehow an "r".

Consonants that are pronounced but unmarked in spelling are relatively uncommon. There are a finite number of historical sound changes, and most of them involve either transforming one sound into another (assimilation; dissimilation) or removing the sound from a word (elision or deletion). ("Historical Sound Changes," Nativlang.com)

Adding a sound to a word is known as epenthesis. In many cases, consonants added as a result of epenthesis result from dialect features like rhoticity (ThoughtCo). While we often think of "r" being dropped in dialects (Boston: "Pahk the cah in Hahvahd Yahd"), sometimes they are added. In the American South, I grew up with "sherbert" for the word "sherbet"; the pronunciation is common enough for Merriam-Webster to describe it as a variant.

Non-dialect epenthesis resulting in an un-spelled but pronounced consonant is less common, since our spelling system was standardized relatively recently. So sounds like the "p" in pumpkin (historically also pumkin according to the OED) are marked in the spelling.

Here are a few other examples that show a range of consonant insertions:

• "warsh" for wash (placed in the Mid-US in this SE question)


• "hain't" for ain't (Appalachian English)


• "drawring" for drawing (British English, passim)


• "hampster" for hamster (common; Merriam-Webster notes the /p/ option)


• "warmpth" for warmth (common; again, M-W notes the optional /p/)

Do you count words borrowed from another language that pronounces consonants differently? If so, I'd nominate pizza, which in American English is pronounced with a T (peet'-za).

There's also the common pronunciation of "sandwich" as "samwich", but that's a replacement, not an insertion.

Merriam-Webster Online includes "mis-ˈchē-vē-əs" as a nonstandard pronunciation of mischievous, and has no entry for "mischievious".

People sometimes add an L sound to the word 'saw' when it's followed by a word that begins with a vowel, e.g., "I sawl it." This is common in south New Jersey.

Segue comes to mind, pronounced /ˈseɡ.weɪ/.

In UK people sometimes add an 'h' in front of words beginning with a vowel.

They are people who habitually "drop their aitches" at the start of a word, so they might say

I 'appen to 'ave five 'undred quid

and because, to them, that is the perfectly normal way to speak, they sometimes add an unnecessay 'h' to words that don't need one, as a mockery of "lardy-dardy" people who "talk posh". So they might say

Have you got hany happles?

and pronounce the first 'H' when they normally would not. I have even seen it in writing, such as this notice on a door

Please knock has the bell will frite the parot.

although in this case the spelling mistakes show a lack of education, not mockery, and the message was written in the same way it would be spoken.

Nuclear, which is often pronounced (wrongly!) with an extra syllable in the middle, more like ‘nucular’…

The English city Bristol was originally called "Bristow" (in Middle English "Bridgestow", in Old English "Brycgstow"), but locals have/had a habit of adding an "l" to words ending with vowels, so it ended up being called "Bristol". To be more precise, the "l" sound is more of an extremely rounded "aw", apparently, which sounds to most ears like an "l".

Some inhabitants also speak an English dialect known colloquially as Bristolian (or even more informally as "Bristle" or "Brizzle"), in which an L sound is appended to words that end in an 'a' or 'o' (thus "area" becomes "areal", etc). This unique dialectal idiosyncrasy is known as the Bristol L (or terminal L).

https://www.bristol.org.uk/about/dialect/

In summary, that's a word that was pronounced with an extra letter that wasn't in its spelling, but now is, in order to spell it how it's pronounced.

The wikipedia entry is quite well written on this matter.

A pretty significant fraction of Americans (including myself) often pronounce both as bolth. I'm not a linguist, so I don't have a source to quote here, but it's common enough that I have had two random conversations on the topic.

The added l isn't quite as strong as if you actually tried to pronounce a word spelled bolth, but it is at least half of an l sound.

I am guessing that the OP is probably more interested in cases where the naive pronunciation is incorrect (i.e., where you must pronounce an extra consonant in order to be understood), in which case this example doesn't apply. But I thought it was worth mentioning anyway.

Edinburgh (/ˈɛdɪnbərə/)

(Geographical names are somehow particular, but they are not excluded explicitly by the original question.)

Do place names count?

There is a place called Cogenhoe in Northamptonshire (UK) which is pronounced /ˈkʊknoʊ/, at least by the locals.

I'm a particular fan of "feud" and "fuel". Both have the same mysterious "y" sound with no obvious connection to the spelling.

The name "Stephen" is pronounced as "Steven", that is, "ph" is pronounced "v", which is unexpected.

Some notes:

• "ph" is normally pronounced "f", and both "v" and "f" are labiodental fricatives, so this strange pronunciation doesn't come entirely out of the blue.


• The name can also be spelt "Steven" (e.g. Steven Tyler), thus matching the pronunciation.


• Admittedly, this is not exactly what you are asking for (it's like "colonel", where "lo" is pronounced as an "r"), but since you consider colonel "in an adjacent neighbourhood", you might be interested in "Stephen" as well.