Greek for 'not even' — from 'an-' (not) + 'homalos' (even), literally something that refuses to be level.
Something that deviates from what is standard, normal, or expected.
From Latin 'anomalia,' from Greek 'anōmalía' (unevenness, irregularity), from 'anṓmalos' (uneven, irregular), composed of 'an-' (not) + 'homós' (same, even), from PIE *somHós (same), from the root *sem- (one, together). The word entered English in the 1570s meaning 'deviation from the common rule.' The PIE root *sem- is extraordinarily productive: it gave Latin 'similis' (similar), 'simplex' (simple), 'singulus' (single), Sanskrit 'samá' (even, same), and Old English 'sam-' (together). Greek 'homós' also produced 'homogeneous'