Woody Guthrie's Happy Joyous Hanukkah was created in 2006-08.
Happy Hanukkah = Hau'oli Hanuka
Happy Hanukkah= Boldog Hanukka
Just like this: Happy Hanukkah
The word "Happy" is English and the word "Hanukkah" is Hebrew.
Joyous or happy = same'akh (שמח)
חנוכה שמחSee also: More about Hanukkah
"... and Happy Hanukkah!"
yes
Yes.
You shouldn't. Hanukkah and Christmas are no necessarily on the same day, so it would be inappropriate to wish someone a happy Hanukkah on December 25, if that day isn't during of Hanukkah. A better idea would be to look on a calendar to see when Hanukkah falls, then then wish your Jewish friends a Happy Hanukkah on Hanukkah.
Happy
Joyful, happy and jubilant