Ah...my next guess was "things to follow", actually, because I knew "secundus" was related to "sequence", "segue", etc.
In English, the word for "second" was originally "other", before the borrowing from Old French, so that's why I guessed that.
Random etymology tangent:
"First" is a pretty interesting word. We know the word "fore", meaning "front", "before", etc. "First" is actually a superlative of "fore":
fore | fore-more (former) | fore-most, forst (first)
Incidentally, "former" was in common use in Old English to mean "first", contrasted with "other". ("Latter" of course comes from "later"). "Next" is a superlative also:
nigh | nigher (near) | nighst (next)
But of course, now we have the more regular series "near", "nearer", "nearest". German preserves the old series:
nah | naeher | naechst
Combine "nigh" with an old word "bide", meaning "to dwell" (related to "bor" in Old Norse, and also to "be"), using the agent form in -r, "bor" (one who bides), and you get: "neighbor" - "one who lives nearby".
The German word for "first", incidentally, is "erst", which is related to the English "ere" ("earlier", "before"), and also a superlative.