"Fruit of the Loom". Is an old company, that borrowed part of the phrase from the biblical term of "fruit of the womb", which refers to a child or children.
The word play change to "Loom" was to reflect the woven textile product that underwear is made from.
I could speculate that the founder was symbolically implying that their underwear held the genitalia necessary for children to exist. This is just my take on it, since it seems meaningless and strange otherwise.
I only purchase and wear "Fruit Of The Loom" brand underwear.