Meaning

adjective slightly open

originFrom Middle English ajar, on char (“on [the] turn”), from on (“on”) + char (“turn, occasion”), from Old English ċierr, cyrr (“turn”), from ċierran (“to turn, convert”), equivalent to a- + char. Akin to Scots char, chare (“to turn, cause to turn”), Dutch akerre, kier (“ajar”), German kehren (“to turn”). See char.

Etymology from Wiktionary, CC BY-SA 3.0