And then there's "an historic event" with a historically British pronunciation, which sounds like a weird non-intuitive exception to Americans, because Brits drop the voiceless glottal fricative "h" sound and start the word with the vowel "i", like "an 'istoric event". Saying "a historic event" by pronouncing the "h" sounds natural to a non-pedantic American (even though it's against the official rules of British English), because Americans pronounce the consonant voiceless glottal fricative "h" instead of dropping it.

https://www.thesaurus.com/e/grammar/an-historic-vs-a-histori...

https://en.wikipedia.org/wiki/H-dropping

H-dropping

H-dropping or aitch-dropping is the deletion of the voiceless glottal fricative or "H-sound", [h]. The phenomenon is common in many dialects of English, and is also found in certain other languages, either as a purely historical development or as a contemporary difference between dialects. Although common in most regions of England and in some other English-speaking countries, and linguistically speaking a neutral evolution in languages, H-dropping is often stigmatized as a sign of careless or uneducated speech.

The reverse phenomenon, H-insertion or H-adding, is found in certain situations, sometimes as an allophone or hypercorrection by H-dropping speakers, and sometimes as a spelling pronunciation or out of perceived etymological correctness. A particular example of this is the spread of 'haitch' for 'aitch'.

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H-insertion

The opposite of H-dropping, called H-insertion or H-adding, sometimes occurs as a hypercorrection in typically H-dropping accents of English. It is commonly noted in literature from late Victorian times to the early 20th century that some lower-class people consistently drop h in words that should have it, while adding h to words that should not have it. An example from the musical My Fair Lady is, "In 'Artford, 'Ereford, and 'Ampshire, 'urricanes 'ardly hever 'appen". Another is in C. S. Lewis' The Magician's Nephew: "Three cheers for the Hempress of Colney 'Atch". In practice, however, it would appear that h-adding is more of a stylistic prosodic effect, being found on some words receiving particular emphasis, regardless of whether those words are h-initial or vowel-initial in the standard language.

Some English words borrowed from French may begin with the letter ⟨h⟩ but not with the sound /h/. Examples include heir, and, in many regional pronunciations, hour, hono(u)r and honest. In some cases, spelling pronunciation has introduced the sound /h/ into such words, as in humble, hotel and (for most speakers) historic. Spelling pronunciation has also added /h/ to the British English pronunciation of herb, /hɜːb/, while American English retains the older pronunciation /ɜrb/. Etymology may also serve as a motivation for H-addition, as in the words horrible, habit and harmony; these were borrowed into Middle English from French without an /h/ (orrible, abit, armonie), but all three derive from Latin words with an /h/ and would later acquire an /h/ in English as an etymological "correction".[13] The name of the letter H itself, "aitch", is subject to H-insertion in some dialects, where it is pronounced "haitch". (In Hiberno-English, "haitch" has come to be considered standard, consistent with its not-an-H-dropping dialects).[14]