The story
From Siam (“historical name of Thailand”) and Cantonese 吊 (diu3, “to hang”), referring to the flower garlands.
Etymology from Wiktionary, CC BY-SA 4.0.
siam diu
Today it means: A Thai-themed nightclub or disco at which people dance to music and pay a hostess to talk to or drink with them by buying her a flower garland. Full definition →