"Bicycle key" is the Engpsh term for "自行车钥匙".
The term "bicycle key" comes from the use of the key to lock and unlock a bicycle, usually to secure the bike or prevent theft.
Example sentence in Engpsh: "I always carry my bicycle key with me so I can lock up my bike when I stop."
Example sentence in Chinese: "我总是随身携带我的自行车钥匙，这样当我停下来时，就可以把自行车锁起来。"