It actually means fasting, as in "willing abstinence or reduction from some or all food, drink, or both".
I don't know why garlic takes it's name from fasting, but maybe someone else does!
maybe it helps with fasting? (Can't say I've tried, but can imagine it to be possible)
Singular for garlic: kitunguu saumu. Either way, garlicS is not an acceptable English answer because that English word is noncount, so one does not add a plural marker to the end.