Pyjamas or Pajamas?

This word came into English from Urdu, although its roots are in the Persian pāy 'leg' + jāma 'clothing'.  Its earliest uses in English refer to loose draw-string trousers made of cotton or silk, worn in some Middle Eastern and Asian countries.  The word first appeared in English in the early 19th century in a range of spelling forms, including such exotics as paunjammahs, paejamus, paijamahs, peijammahs, pigammahs; later in the 19th century the modern forms pyjamas and pajamas began to appear, along with pyjammas, which is still common today.  The -s was added to the word by comparison with words like trousers and drawers; the singular forms pajama and pyjama are sometimes found, especially in compounds like pyjama-party, or pyjama-top.  Other examples recorded in the early 20th century include pie-jim-jams - which survives today as jim-jams - and a shortened form: pyjams, used by John Betjeman in Summoned by Bells (1960).  Today pyjamas is the standard spelling in UK English and pajamas is the standard US spelling.