Depends which one you mean.
Cellar Spider - Pholcus phalangioides
Crane Fly - Tipula paludosa
Harvestman - Phalangium opilio
The scientific name for a daddy long leg is Pholcus phalangioides.
It depends what species you are referring to. There is the crane fly. It's scientific name is Nephrotoma.You are probably referring to the cellar spider or the harvestmen. The cellar spideris most likely the spider you are talking about. It's scientific name is Pholcus phalangioides. There harvestmen's scientific name is Hadrobunus grandis.
The daddy long legs is named for its incredibly long legs, which are massive in comparison to its body.
The name daddy-long-legs beginning is unknown. It is suspected to have come from a book by Jean Webster about a girl in an orphanage whose benefactor is a tall man whom has long legs and she calls him Daddy Long Legs.
Daddy long legs or Pholcus phalangioides
Daddy long legs
Cranefly
None of the species know by the common name "daddy long legs" have gills, nor do they live in water and have need of them.
Another name for the "Crane fly" is the "Daddy long legs"
It is the common name for a really long legged spider (arachnid).
harvestman spider
Spiders usually have two body-parts while daddy long-legs have only one. Daddy long-legs have a teeny body with very long and thin legs, hence the name. Some spiders might have long legs and small body but you'll never find one as scrawny as the daddy long-legs. You can find daddy long-legs in groups sometimes while spiders are always alone. Spiders defend themselves by biting. Daddy long-legs spit acid and cannot bite, they're fangs are too small to penetrate skin.