The reason I know exactly what it means is that that was what I meant by it in 1949 when I was three years old. It was such a useful word, with no exact synonym, that it continued in family usage and spread to friends when I was older. My circle was certainly using it at university in the second half of the 1960s.
I can think of these possibilities:
1. It is such an obvious word that it has sprung up more than once.
2. It has spread from my original use.
Can anybody shed any light? For example, instances of its use before 1965 or thereabouts?
ETA The key part of the meaning, very conspicuous in both contexts, was physically inserting oneself, somewhat surreptitiously, but not necessarily with the lateral movement implied by "wiggle". And that's exactly how I used it in the 1940s.