'symmetrical-leaved' is a modern English compound formed from 'symmetrical' + 'leaved', where 'symmetrical' relates to 'symmetry' (balanced proportion) and 'leaved' indicates 'having leaves'.

'symmetrical' comes into English via Late Latin/French from Greek 'summetria' (συμμετρία) meaning 'joint measure' (from 'sym-' together + 'metron' measure), while 'leaf' comes from Old English 'lǣaf' (Proto-Germanic *laubą). These elements combined in modern English to form descriptive compounds such as 'symmetrical-leaved'.

Individually, 'symmetry' originally expressed the idea of 'measured-together' or proportional arrangement and 'leaf' simply meant 'leaf'; over time the compound has come to be used specifically to describe plants whose leaves are balanced or mirror-like in shape or arrangement.