Is there a specialised term for words that are almost always mispronounced?

With few exceptions, I hear people pronounce enmity emnity, Wednesday Wensday, and prerogative perogative.

Is there a proper term for this phenomenon?

Consider, metathesis

(phonetics, prosody) The transposition of letters, syllables or sounds within a word, such as in ask as /æks/. Wikipedia

nucular is a commonly used metathetic form of the word nuclear Wikipedia

Just come across the word which describes the mumbling of Wednesday & prerogative.

Lenition (Oxford Dictionaries /US English) The process or result of weakened articulation of a consonant, causing the consonant to become voiced, spirantized, or lost.

In UK English a more limited definition is given.