In a Facebook comment on my latest mishearing posting, Billy Green offered an example that is surely not a mishearing, but might be an eggcorn or a lexical confusion: sum up for summon up. Billy’s example:
Today, I finally summed up the courage to break up with my abusively controlling girlfriend. I don’t know what I was thinking, but instead of leaving as a free man, I left as an engaged one. (link)
Not in the ecdb, but it came up on the Eggcorn Forum in 2007. And the reverse subtitution, summon up for sum up, came up there in 2010. Commenters characterized the first as an eggcorn, but the semantic relationship is unclear.