effect [LME] Effect ‘result, consequence’ is from Latin effectus, from efficere ‘accomplish, work out’, formed from ex- ‘out, thoroughly’ and facere ‘do’. Its negative is defect [LME], while deficit [L18th] is from Latin deficit ‘it is lacking’, from the verb deficere, although deficiency is Late Middle English. Deficit was used formerly in inventories to record what was missing. Feckless [L16th] ‘lacking in efficiency or vitality’ is based on Scots and northern English dialect feck, a shortening of effeck, a variant of effect.