Quote
C Chiu
According to 廣州話普通話詞典 (p.413), 星 [sing1] means “to slap” with the example phrase 星你兩巴. That ‘s what I’ve often heard, and I haven’t heard of 醒[sing2]你兩巴. I believe 醒 is confined to the meaning of “give as a gift”.
Apart from the above source, I can’t find any other source references on 星 and 醒 in relation to the meaning “to slap”.
As regards 兜巴星 [dau1 baa1 sing1], I suspect that this common expression is the abbreviated form of 兜口兜面一巴星過去 (to slap right on the cheek).
A reasonable guess of 星 as " to slap" is from idiom 「金星直冒」( seeing stars) this phrase is almost exclusively for describing the reaction of "someone being slapped or clobbered"
Or as I suggested, the 「醒」in「醒你兩巴」 ( gift you two slaps) was tone changed as 星，and the dictionary editors read the sentence as " to s,sp you twice" and mistakenly listed 星 as "to slap"
In either case, the usage of 「星」as "to slap" is commonly used enough to justify having the said definition. But the phrase「醒你兩巴」as " give you two slaps as a tips" does make sense.
My personal experience with 醒你兩巴:
My father often said to me: 「你仲駁嘴？係咪要我醒你兩巴？」in his mind, slapping me was his grace to me because he's teaching me a lesson.