The story
A variant of the British 999, originally selected as an appropriate number for rotary-dial telephones and adapted in New Zealand because the formatting on its pulse-dial system made 1 equivalent to 9 as processed by its British-made telecommunications equipment.
First known use, by meaning
- 1956 The telephone number for emergency services in New Zealand and Nauru.
Etymology from Wiktionary, CC BY-SA 4.0.