I was told that “Altenbaugh” is loosely translated as old tree, or something like that. Is that accurate?
It's hard to answer this question without knowing the place where this name occurs.
Regarding German words, then only the first half is translatable: "Alten" is a form of "alt" and means in deed "old". But "baugh" has no german equivalent.
But (inspired by the comments) I also found a website which gives detailed explanations of names. Unfortunately the whole name "Altenbaugh" can not be found, but its two halves. According to this website
- "alten" comes from the Old English awiell, which means enclosure or settlement.
- "baugh" was initally a nickname for a small or short man, derived from the Welsh word "bach," which means "little".
So in conclusion it seems that the surename "Altenbaugh" can loosely be translated as "tiny settlement".
The person who told you that simply guessed that "alten" is German (and means old) and that baugh might be related to German Baum (=tree).
I think that the person is right with alten, but I would be surprised, if German "Baum" had changed to "-baugh". Like Janka and others I priviledge another word as source: Bach (in German) or beek (in Dutch) which could have become "-baugh" after anglicisation. The name would mean something like "old creek".
Today there exist at least two Altenbach in Germany (in Saxony and Baden-Wurttemberg). A Saxon settlement in England could have been named the same and become "Altenbaugh" in the course of time. It's also possibly that a German immigrant with name Altenbach is at the origin of the surname Altenbaugh.
(This is my guess, which is only slightly better than what the person told you.)