h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

The cult of Christianity worshipping Mary is probably the reason.

"translations of a Hebrew name of the 1st Century AD, which came into Greek as Iohannes and from there into English (John) and Irish (Eoin)." It's Yohanan (God's pardon, grace or gift) in Hebrew, pronounce Yo-Cha (ch like the sound in loch)- Nun.
Mary come from Miriam (not sure on meaning).
Magdalene is from Migdal (tower; the place still exists today, a small town).

Ya'el, my first name, is a biblical heroine and also a wild mountain gazelle. Means something like elevation, improvement, making something more efficient.

Regarding nicknames - Gnomon said the names with O added to them arent shorter than the original name, after mentioning Declan -->Deco.
How about female marital names?
The russians used to change a woman's married name but move it to the female form, which is why Anna, who married Mr Karenin, is now Karenina. I find that sort of thing very intriguing.

...and lastly, Randy is short for Randal, methinks?

Elly

Or Randolph.

~jwf~