This is speculation but I wonder if both of you have an unusual form of synesthesia, which is not a pathology.

Its most common form is colour synesthesia; "seeing" in your mind different letters and/or numbers associated with different colours - A might appear green, B might appear blue, 4 might appear red, 7 might appear yellow, etc. There are many forms of it; probably about 4% of the population experience it.

What you both experience, "seeing" a visual image of a word or concept could be a form of synesthesia.