on/at first acquaintance

: preceding all others in time, order, or importance: such as

: earliest

: being the lowest forward gear or speed of a motor vehicle

: before another in time, space, or importance

: in the first place

: for the first time

: one that is number one in a series — see Table of Numbers

: something that is first: such as

: the first occurrence or item of a kind

: the state of being acquainted

: personal knowledge : familiarity

: the persons with whom one is acquainted