I understand the word "remain", but I cannot understand why it's remina-nts, it looks like someone incorrectly write down the word re-main into re-mina, so hilarious.... Not to be offend because I know nothing about it, but I'm very willing to understand the story behind the scene!
To add more detail to Josh B.'s answer:
remain (v): early 15c., from Anglo-French remayn-, Old French remain-, stressed stem of remanoir "to stay, dwell, remain; be left; hold out," from Latin remanere "to remain, to stay behind; be left behind; endure, abide, last" (source also of Old Spanish remaner, Italian rimanere), from re- "back" (see re-) + manere "to stay, remain" (from PIE root *men- (3) "to remain"). Related: Remained; remaining.
remnant (n.): late 14c., contraction of remenant (c. 1300), from Old French remanant "rest, remainder, surplus," noun use of present participle of remanoir "to remain" (see remain (v.)).
It seems that your objection is accurate -- the original word was indeed remenant, but 600 years or so ago it was contracted to the modern remnant for reasons no one now knows. These things happen.