In American English "cuckoo" means a little bit crazy. It's not real derogatory, more a humorous term.
In BE, the cuckoo was the symbol of marital infidelity-- by "was," I mean back in Medieval and Elizabethan times. Like Cowbirds, Cuckoos lay their eggs in the nests of other birds, and leave the care of their young to other hens, whose instincts cause them to nurture any chicks that hatch in their nests.
By analogy, a man whose wife "cuckolded" him, meaning she had a child by another man, ended up raising children not his own. If this situation were known around the village or town where he lived, he might get taunted by other men about it. They might make "cuckoo" sounds when he walked by.
amazing! I happened to read a article in Chinese today about cuckoo , which reveals the despicable behavior of them.
Yet conventionally, cuckoo is regarded as the harbinger of spring for the sound it makes resembles "planting seed " phonetically in Mandarin.