Initial comes from Latin initium meaning 'a beginning', literally 'a going in' — from inīre, 'to enter'. To begin something is, etymologically, to step through a door. The same root gives us exit, transit, circuit, and ambition.
Existing or occurring at the beginning; first in a series or sequence.
From Latin initiālis meaning 'of or pertaining to a beginning', from initium meaning 'a beginning, an entrance, a start', from inīre meaning 'to go in, to enter upon, to begin', from in- 'into' + īre 'to go'. The metaphor is spatial: to begin something is to go into it, to cross a threshold. The same root gives us initiate (to start someone on a journey), initiative (the first step), and commence (which comes from a different Latin root but carries
The Latin root īre ('to go') hides inside dozens of English words that seem unrelated. An exit is a 'going out'. A transit is a 'going across'. A circuit is a 'going around'. An ambition is a 'going around' — from Roman politicians who went around canvassing for votes. And an initial is a 'going in' — to begin is to step through a door