from The American Heritage® Dictionary of the English Language, 4th Edition
- interj. Slang Used as a greeting or to attract someone's attention.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- interj. A greeting similar to hi.
- interj. An interjection similar to hey.
- interj. Present! Here!
- contraction of you and are
- pro. shortened form of your.
- pro. third-person singular, familiar
from The Century Dictionary and Cyclopedia
- An exclamation noting effort: usually joined with ho or O.
- A dialectal variant of you.
From Middle English yo, io, ȝo, yeo, yaw, variant forms of Middle English ya, ye ("yes, yea"), from Old English ġēa ("yes, yea"). Compare Danish, Swedish, Norwegian jo ("yes"). More at yea. (Wiktionary)
From you're, your, etc. (Wiktionary)