'equal-toothedness' originates from Modern English, specifically a compound of the adjective 'equal' (ultimately from Latin 'aequālis'/'aequus' meaning 'even' or 'level'), the noun 'tooth' (from Old English 'tōþ' meaning 'tooth'), and the nominalizing suffix '-ness' (from Old English '-ness', meaning 'state or quality').

'equal-toothedness' was formed in Modern English by combining 'equal' + 'tooth' + '-ness'. The element 'equal' came into English via Old French from Latin 'aequālis', 'tooth' comes from Old English 'tōþ', and '-ness' is an Old English suffix; these components were compounded in Late Middle English/Modern English to yield the modern descriptive noun.

Initially the components separately meant 'even' (equal) + 'tooth' + 'state/quality' and over time they have been combined to denote specifically the dental characteristic 'having teeth of equal size or form', largely retaining the literal sense but used as a technical descriptor.