'balky' originates from Old English/Middle English roots of the noun 'balk' (Middle English 'balke'), with the adjectival suffix '-y' added to form 'balky'.

'balk' existed in Old English as 'balca' meaning a ridge or beam; it developed in Middle English as 'balke' meaning a beam, ridge, or an obstruction, and from that sense the verb 'to balk' (to stop or refuse) arose; the adjective 'balky' then formed from 'balk' + '-y', and 'balkier' is simply the comparative form.

Initially, 'balk' referred to a physical beam or barrier; over time it gained the figurative sense 'to stop short or refuse to proceed,' and 'balky'/'balkier' now mean 'inclined to refuse or resist.'