Sananmuunnos ("Word transformation"), sometimes kääntösana, is a sort of verbal play in the Finnish language, similar to spoonerisms in English.
Special to Finnish is a narrow phoneme inventory and vowel harmony.
Much of practical sananmuunnos wordplay revolves around obscene double entendre expressed by spoonerism.
Initial morae of two adjacent words are exchanged, which is spoonerism by definition.
Typically presented, spoonerisms are a kind of double entendre.