You know how you feel when you can’t open a jar of pickles? And then grandma walks in and does it in one shot without even grunting? That’s called feeling feeble, or lacking strength.
In fact, feeble, comes from the Latin word flebilis, which means "lamentable" or "unsatisfactory." But don’t let it get to you. Your puny, inferior muscles are nothing compared to the guy who makes feeble attempts at humor. Lame-o jokes are way more lamentable than inadequate biceps.