Howdy
Okay we all know when Lion-O needs assistance or wants to extend to Sword of Omens or wants to shoot something out of the Sword he will always say HO! Why is this? What is the siginifigance of saying HO? Has these been detailed anywhere? Fanzines, comics, card backs…anywhere?
Thanks for any theories and answers?
Chris M
I believe that it comes from Heigh-ho, or Hi-ho as a few songs went.
Back in the Klondike days miners would shout Heigh-Ho when they
struck gold, I think it was ment as a level of excitement to boost
morale of those not getting anything. It was later used in Snow White
and theSeven Dwarves in a song, as well as Heigh-Ho silver oh, and
a few others.
When Leonard Starr began writing the original treatment for the movie,
(The bible that is seen in the exclusives section of the site.) he did not
mention any further explination on the phrase. My guess us when the
show was in pre-production the writing staff was to come up with a
catch phrase to use, and he chose “Heigh-Ho” Dropping the “Heigh”
part.
It could signify a level of excitement, and raise morale, and possibly
be used for that reason.
That is the best I can come up with.
Sounds good to me lol 
Chris here…
I think Tim’s explanation is probably pretty close - in reality, I suspect “ThunderCats Ho!” was chosen simply because, well, it feels like a great thing to shout! Open your bedroom window now and shout “THUNDERCATS - HOOOOOOOOOOOOOOOOOOOO!!!” down your street as loud as you possibly can. If you don’t feel silly, you’ll feel brilliant! 
Take care…