These two phrases are from Harper Lee's Go Set a Watchman. I'm not sure, but I guess the first one (light'ud knots) is talking about a woman who can handle problems easily and is kinda independent. As for 'hind f'omus, I guess Jim is right in his comment below that it must be "behind from us".
Here are the paragraphs:
Don’t you know how to catch a woman, honey? Women like for their men to be masterful and at the same time remote, if you can pull that trick. Make them feel helpless, especially when you know they can pick up a load of light’ud
knots with no trouble. Never doubt yourself in front of them, and by no means tell them you don’t understand them.”
and
You’re sort of ’hind f’omus, Miss Scout. You sort of haven’t caught up with yourself … now if you’d been raised on a farm you’da known it before you
could walk, or if there’d been any women around—if your mamma had lived you’da known it—”
Best Answer
I suspect light'ud knots is supposed to be a contraction of lightwood knots. You can Google, and find the alternate spelling light'ood knots.
"Lightwood knots" are knots of pine wood that burn easily.
The Dictionary of Regional American English has many regional expressions for:
Two names for these given in DARE are lightwood knots and lighterd knots. In a non-rhotic dialect (found in Southern dialects and AAVE), light'ud knots and lighterd knots would be pronounced very similarly.
For "'hind f'omus", I expect it can't be figured out except by context. Lack of context is why your question is being downvoted and in danger of being closed. Please give the few sentences where you found this expression.