Think of something shaken lightly over a wide surface: a few drops on a dry road, a few people in a big hall, a few herbs on a plate. There is something there, but the gaps are bigger than the things. Both uses of smattering are that same thin — once over a space, and once over what a person knows.
The supplied source gives only the word's build: smatter plus -ing. The old verb smatter has almost dropped out of use, and smattering is what remains of it, so the noun is best learned whole.
來源資料只給了組成方式：smatter 加 -ing。舊動詞 smatter 今天幾乎不再單獨使用，smattering 是它留下來的形式。來源沒有說明 smatter 本身的意思，所以這裡不多推論，把這個名詞整個記起來就好。
Wiktionary entry supplied in this packet (source_ref kaikki:3f6f69a190036ae4:1300857565): ‘From smatter + -ing.’ No gloss for the base verb is supplied.
Two branches
空間上的一點點
核心畫面本身：東西散在一片空間上，少而且有空隙。
noun · C1
A small number or small amount of something, spread thinly rather than gathered together, and usually less than you expected or less than would be enough. Nearly always used as ‘a smattering of’ before a plural noun or an uncountable noun.
零星少量
知識上的一點點
把同一層薄薄的撒開挪到腦袋裡：知道的東西零星分布，連不成一片，所以不夠用。
noun · C1
To know only a little about a subject — enough to say or recognise a few things, but not enough to really use it. Most often said about a foreign language.
略懂皮毛