While reading https://wiki.python.org/moin/TimeComplexity
A double-ended queue (abbreviated to deque, pronounced deck, like “cheque”) is an abstract data type that generalizes a queue, for which elements can be added to or removed from either the front (head) or back (tail).
Deque is sometimes written dequeue, but this use is generally deprecated in technical literature or technical writing because dequeue is also a verb meaning “to remove from a queue”.