Pyjamas is the British spelling of what Americans write as pajamas, and the y is the giveaway that somebody was reaching for a classical look. The word is not Greek at all — it comes from Persian and Urdu, from words meaning "leg garment" — but English spellers, confronted with a foreign vowel, reached for the y they associate with learned words like myth and system.
The early English attempts are a good record of people writing down a word they had only heard: pai jamahs in 1800, pigammahs in 1834, peijammahs in 1840. It took decades to settle, and it never fully did — the two national spellings preserve the disagreement. The word belongs with bungalow, jungle, shampoo, loot and thug in the vocabulary the British brought back from India, and it is the only one of them where the spelling looks classical by accident.
pyjamas (n.) also pyjama (adj.), chiefly British English spelling of pajamas . Early spellings in English also include pai jamahs (1800); pigammahs (1834), peijammahs (1840).
pyjamas came in through Later and wider borrowings, and its spelling follows that family's conventions.
What gives it away on the page
| everyday domestic words from India | Sanskrit-descended languages, via the Raj.shampoo, bungalow, jungle, pyjamas, loot, thug, guru |
Later and wider borrowings in the spelling guide · guess another word's family