耷濕 means shabby; simple and crude. "This term is used in Cantonese, not Mandarin/Standard written Chinese." Wiktionary says the same thing.
But 耷 means "big ear" (noun) or "droop" (verb). 濕 means "damp". Neither means "simple, crude, shabby". Then where does this meaning stem from?
Googling "wet droop" showed me this picture of "drooping wet tree leaves on a rainy morning". Is this germane?