What are the origins of the word 'happy'?

From Online Etymological Dictionary:

hap

c.1205, "chance, luck," from O.N. happ "chance, good luck," from P.Gmc. *khapan (source of O.E. gehæp "convenient, fit"). Meaning "good fortune" is from c.1225.

Where:

c. = circa or "around"

O.N. = Old Norse

P.Gmc. = Proto Germanic

O.E. = Old English