I did a search for pages in Japanese. Most of the references use katakana to write both names, which usually (not always) means that it’s a made up word with no clever kanji, or it’s a foreign word. We can easily dismiss option 2 since it’s pretty obviously a Japanese word, not a borrowed one. The movie used fuchikoma (ƒtƒƒRƒ}) while the TV series had to use *tachikoma* (ƒ^ƒƒRƒ}) for what are, apparently, legal reasons. The design of the tanks is also different in the series and the movie for the same reasons.
Thus ends the short answer to this question: it’s probably just something that they made up.
I was curious, so I spent some time looking for other stuff. May the gods help me, my curiosity is going to kill me someday.
Most seem to think that there’s no meaning to the words, but one site has a proposed list of references that they feel the author of the original manga was trying to make with character names. They propose, with a self-assessed high level of confidence, that fuchikoma were meant to refer to an old myth about Amaterasu Oomikami (the Japanese Sun-Goddess) and her brother Susanowo (Storm God, with a combined major in bad manners).
The stories are told in titled episodes, one of which is called Ame no Buchi-koma (“V‚Ì”Á‹î) or “heavenly spotted horse” or “spotted horse from heaven.” The /f/ sound is changed to /b/ in some intances in Japanese. A straight reading of the character, without the ame no is fuchikoma. The kanji used for horse is an elegant usage according to my dictionary, so a different translation for “horse” could be “steed.” Incidentally, this character is also used for pieces in Japanese chess («Šû).
I searched for the story, but like most myths there are different versions and the language is archaic. If I screw things up and you know better, correct me please. Apparently, a horse (possibly one belonging to Amaterasu Oomikami; it’s not clear in the story) was skinned by Susanowo, who grabbed the horse’s tail and pulled until the skin came off inside out, like taking off a shirt. He then stuffed the hide into her weaving place through a hole or crack in the wall, causing her weaving-women to panic, which resulted in some injuries. Considering his earlier bad behavior (pissing in her rice fields, among other things) and the violence of this act, Amaterasu Oomikami thought that she was in danger and ran away to hide in a cave. This resulted in the sun going down and not coming up until the other gods eventually tricked her into coming out.
There you have it, more than you ever wanted to know about the possible connection between an incidental usage in anime and Japanese mythology. I don’t see much of a connection other than a coincidence in sounds, which never happens in Japanese. <heavy sarcasm> Maybe I lack imagination, or maybe some Japanese otaku are really stretching things in an attempt to make them fit. I leave that as an exercise for the reader.
