LATCHKEY
latchkey
(noun) key for raising or drawing back a latch or opening an outside door
Source: WordNet® 3.1
Etymology
Noun
latchkey (plural latchkeys)
A key, especially to an outside door.
Synonym: check key
A child who is given a key to the home and is expected to remain at home alone (without adult supervision until the parents return from work).
Adjective
latchkey (not comparable)
Equipped with a key; generally in the phrase latchkey child.
Source: Wiktionary
Latch"key`, n.
Definition: A key used to raise, or throw back, the latch of a door, esp. a
night latch.
Source: Webster’s Unabridged Dictionary 1913 Edition