Blackjack players can "double down" after receiving their initial two cards.
What is the past tense of 'Double Down'?
Double down is an idiomatic phrase which is also a phrasal verb. Phrasal verbs are defined as follows:
There are three main types of these phrasal verbs, depending on what the phrase contains. The types are:
In order to form the past tense of any of the phrasal verbs, one must put the verb into the past tense. For example:
The phrase double down can be broken into the verb double plus the preposition down, so it is a prepositional verb phrase. The past tense of "double" is "doubled", so the past tense you're asking for would be doubled down.
A similar example of creating this past tense is double over--you would say that someone doubled over in pain, but not doubled overed or doubled overed.
Common usage is doubled down. Some examples (mostly not related to blackjack, but using the term in a figurative sense):