Give me some "holy sh... did that just happen" ideas

[Schallmoser]

In fact the real origin of horrido seem to originate in the very old German hunting tradition. Back then the hunters would say "hoch Rüde hoch" which means "get up my dog, get up".
Till today horrido is commonly used as a greeting between hunters in Germany.

Concerning military e.g. Luftwaffe, but also in ancient times horrido is and was used as battle cry.

here is the link to the german wiki page with more reference:
http://de.wikipedia.org/wiki/Horrido

Oh, and I forgot, tally-ho seems to have almost the same kind of origin:

Tally-ho dates from around 1772, and is probably derived from the French taïaut, a cry used to excite hounds when hunting deer. Which in turn derives from taille haut![1] meaning raise swords cried by French commanders upon mediaeval battlefields upon the final assault.

ref: http://en.wikipedia.org/wiki/Tally-ho

cheers,
Schallmoser