From daddy + longlegs.

• (British) IPA: /ˈdædɪ ˈlɒŋ(ɡ)lɛɡz/

daddy longlegs

1. (UK, Ireland) The cranefly; any insect of the suborder Tipulomorpha.
   • 2004, Bill Hansford-Steele, African Fly-fishing Handbook‎^{[http://books.google.com.au/books?id=XwPJJO4vOJkC&pg=PA316&dq=%22daddy+longlegs%22+-intitle:%22%22+-inauthor:%22%22&hl=en&sa=X&ei=Fi81T8faCMqViQfz29WjAg&redir_esc=y#v=onepage&q=%22daddy%20longlegs%22%20-intitle%3A%22%22%20-inauthor%3A%22%22&f=false]}, page 316:

     Daddy longlegs adults are weak flyers, falling onto the water surface in the lightest of breezes, and even on calm days.

2. (Australia, Canada, New Zealand, US) Any (non-spider) arachnid of the order Opiliones, mostly with long thin legs; the harvestman.
3. (loosely) The daddy long-legs spider, any spider of the family Pholcidae.
   • 2010, Lou Bensinger, Tiny Invaders in Your Home‎^{[http://books.google.com.au/books?id=jAAZ0BLY8xUC&pg=PA10&dq=%22daddy+longlegs%22+-intitle:%22%22+-inauthor:%22%22&hl=en&sa=X&ei=fyc1T5n4JYTGmQXf2bibAg&redir_esc=y#v=onepage&q=%22daddy%20longlegs%22%20-intitle%3A%22%22%20-inauthor%3A%22%22&f=false]}, page 10:

     Another spider neighbor that is commonly found in homes is the daddy longlegs. The daddy longlegs is often called a cellar spider.

• (insect of suborder Tipulomorpha) cranefly, tipulid
• (arachnid of order Opiliones) harvestman
• (spider of family Pholcidae) cellar spider

• French: faucheur
• German: Opa Langbein, Weberknecht
• Russian: сеноко́сец
• Spanish: segador, falangio