既然
jìrán · HSK 4
since
既 = already + 然 = so/thus → already so, therefore since
既 means already/given that; 然 means so or thus. Together 既然 sets up a logical 'given that X is already the case, therefore...' — the English 'since' or 'now that'.
既 — 皀 (food vessel) + 旡 (person turning away)
Originally a pictograph of a person turning away from a food vessel, signaling a finished meal. From this came the meanings 'already' and 'completed.' The modern sense 'since' or 'now that' developed by extension from the idea of an action already done.