I don’t know it off the top of my hand

This is a mash up of “off the top of my head” and “offhand”, both meaning to say something without preparation.  Hand and head both look and sound similar, and are both body parts, all adding to the confusion.   I have heard this one many times in conversation and in meetings.

I have it on the tip of my hand

This is another classic uttered by “the master”.  I remember he was trying to say “on the tip of my tongue” (a word or phrase that can’t be remembered) just out of reach) but what is the mix-up?  At first I thought it was “at my fingertips” (within reach) but my “ol pal” reminded me that the phrase “tip my hand” (revealed something that was hidden, such as in a card game) was probably the culprit and I agree.  The speaker perhaps was thinking tongue or finger but his unconscious grabbed the wrong body part, as we have seen in prior malaphors.

One hand scratching the other

This is a mix up of two similar meaning idioms – “one hand washing the other” and ” you scratch my back, I’ll scratch yours” (reciprocal help).  These malaphors that mix idioms having the same or similar meaning are also called congruent conflations.

Rule with an iron thumb

I heard this gem from” the master” as he described our boss: “You know, she rules with an iron thumb.”  This is a mash-up of “rule with an iron hand” (harsh leadership) and “under my thumb” (controlling someone).  Both phrases have similar meanings and both contain a similar body part so the mix-up is obvious.  Of course, “the master” also enjoyed The Rolling Stones so it is possible that the song “Under My Thumb” played a little part in his twisted but ingenious mind.  “My ol pal ” noted that “rule of thumb” (a general principle based on experiment) was also probably on ‘the master’s” mind and I agree.  This idiom has the words rule and thumb, so those words were swirling in his head for sure.