Shift is from the builtin command of same name in unix shells. It shifted a command-line argument from the beginning, so that if you used it in a loop, you could loop through command-line arguments in normal order. Even the DOS command.com has copied that command with the same name.

Update: I see jbert has already said this in his reply.

In reply to Re: Why are "push", "pop", "shift" and "unshift" so named? by ambrus
in thread Why are "push", "pop", "shift" and "unshift" so named? by Cody Pendant

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