Why does the name Rebecca mean Becky and Bill mean Will?

[convo_king89]

I’ve always wondered this

[Lliam]

Becky is short for [Re]Becca. The ee sound of a Y or I is applied to the end of many girl's names because has a more diminutive, affectionate, or familiar association in western culture. So Becca becomes Becky, just as Cinthia or Cynthia becomes Cindy or Cyndi.

Will is short for William. I don't know how the W got replaced with B in Bill. It's a British thing. I guess they just rhyme. The explosive bilabial sound of B is more distinctive than W when spoken.
The "labio-velar approximant" sound of a W is softer, requires more breath/projection, requires one to purse their lips as if kissing and, to some ears, may sound less masculine than a hard B.

The one I wonder about is, how did Jack become a nickname for John?

[exitseven]

The one that I could never figure out was cslling somebody named Margaret Peggy/

[convo_king89]

Lol exactly