Debut is French borrowed late, and the silent t at the end is the proof. French stopped pronouncing most final consonants centuries before English took this word in 1751, so English got the spelling with the letter and the pronunciation without it. Ballet, buffet, gourmet and depot all show the same seam, and all arrived in the same late period.
The French word means "first appearance," but figuratively: it comes from débuter, "to make the first stroke at billiards," or to lead off at bowls, from but, "mark, goal." So a society debut is, underneath, an opening shot. The English verb followed in 1830. Fowler was characteristically severe about the pronunciation — the word "can only be pronounced as French, and should not be used by anyone who shrinks from the necessary effort."
debut (n.) "first appearance in public or before society," 1751, from French début "first appearance," a figurative use from débuter "make the first stroke at billiards," also "to lead off at bowls" (a game akin to bowling), 16c., from but "mark, goal," from Old French but "end" (see butt (n.3)). The verb is first attested 1830. Related: Debuted; debuting . Début can only be pronounced as French, and should not be used by anyone who shrinks from the necessary effort. [Fowler] also from 1751
debut came in through Later and wider borrowings, and its spelling follows that family's conventions.
How that family writes these sounds
| a final stressed syllable that just stops | Modern French: write the consonant you can't hear, usually -tballet, gourmet, debut |
What gives it away on the page
| -eau, -oir/-oire, ch said as /ʃ/, silent final consonant | Modern French — borrowed after French itself stopped pronouncing final consonants.bureau, memoir, machine, chef, ballet, debut, gourmet |
Placing it without the spelling
| the stress on the last syllable, and the word simply stops there | Modern Frenchballet, debut, gourmet |
Later and wider borrowings in the spelling guide · guess another word's family