'dual-peaked' is a compound formed from 'dual' + 'peaked'. 'dual' originates from Latin, specifically the word 'dualis' (from 'duo'), where 'duo' meant 'two'. 'peaked' derives from the noun 'peak' (see below).

'dual' entered English via Latin 'dualis' (through Medieval/Latin usage) and retained its numeric sense; 'peak' developed from Middle English forms such as 'pike'/'peke' meaning a pointed top and eventually became modern English 'peak'. The compound 'dual-peaked' is a modern English formation combining these elements.

Initially, the components meant 'two' and 'pointed top' separately; over time, when combined as 'dual-peaked' the phrase came to mean specifically 'having two peaks' (applied both to physical forms and to two-mode distributions).