[[Ergative alignment is an argument coding pattern where the S-argument of intransitive verbs has the same argument coding as the P-argument of transitive verbs but different coding from the A-argument.]]
The term "ergative(-absolutive) alignment" was first used by Plank (1979) and adopted by Nichols (1992). The label "ergative" for the case in this alignment pattern goes back to the early 20th century.
ergative alignment system (STR) = a system in which the S and P roles are expressed with the same form, but the A role is expressed with a different form. Example: in Yuwaalaraay, argument phrases expressing the A role use the Ergative flag -gu, but argument phrases expressing both the S and P roles use the zero-coded Absolutive flag. (Section 6.3.1)
"In this alignment, the case marker coding both S and P identically is referred to as absolutive, while the case marker coding A differently is called ergative (i.e. S = P ≠ A). Not surprisingly, this alignment is known as ergative–absolutive." (Song 2018: 290)