prototonic

adjective

pro·​to·​ton·​ic ˌprō-tə-ˈtä-nik 

1

: characterized by accent on the first syllable

2

of Old Irish compound verbs : stressed on the first element of a verbal form compare deuterotonic

Word History

Etymology

proto- + tonic entry 2

First Known Use

circa 1900, in the meaning defined at sense 1