"Ya" literally means already but in colloquial spanish its used like we use the word "really" "Ya esta muy grande" Ya tengo un dolor de cabeza-anyway the blax and chicanos use the english word already this way as an emphatic-they'll say already by itself to mean "yes i agree" and they'll say "i already hate this crap" not in reference to time but to emphasize-i know you guys be hatin' and dont care but oki might answer this thing anyway...

I thought "Ya" was German.

"Ja" is german-and its also emphatic-but this isnt a german influence

"Ya" also means, "now". BTW, assimilation of Spanish words is nothing new.
"Corral", "rodeo" are Spanish, as are state names of Texas, Colorado, Arizona and California.

no its not new-but the assumption of a foreign word in a grammatical context is unusual,,,