Realistically...this character is less likely to do "spectacularly stupid things" than a high Int/low Wis character would be.
Intelligence is a measurement of...
Mental acuity, information recall, and analytical skill.
These are your scholarly smarts...the sort of smart that makes you do really well in college, or makes you a successful scientist or researcher. This represents how well you can recall information that you have learned, and how good you are at taking complex problems and breaking them down logically into solvable pieces. A character with High Int/Low Wis is your stereotypical Awkward Engineer. The person who can solve complicated calculus problems in their sleep, but has zero ability to read the people around them and are considered to have no Common Sense.
For a Hollywood example of an extreme case...look at the stereotypical 'nerd' character. The one who is hyper intelligent, but just really doesn't seem to grasp how the world works outside of theories and books.
Wisdom is a measurement of...
Awareness, intuition, and insight
These are your practical smarts. The sort of smart that notices details other people miss...that can make intuitive leaps to a good solution, that understands people and how they think. A low Int/high Wis character is your 'street smart' person who is terrible at the scholarly arts and probably couldn't tell you a thing about the history of where they live...but they can read people like an open book and give fantastic practical advice.
In short, think of your typical film 'wise old man.' Y'know, the guy who didn't finish high school, doesn't understand all those fancy gizmos of the modern world...but when the main character hits their wit's end, he's the one that actually has useful advice for them. And he gives it unsolicited, and gives the exact right advice that the character needs at the moment. He's been there. He's lived it. He may not have all the facts and numbers and data, but he understands how the world works. And he understands people...and he can tell what's going on with the main character and knows just what to say to help them.
"Dumb things" done by a High Wisdom/Low Int character are likely to be mistakes of ignorance. They didn't know how a thing works, and so they didn't know how to approach it. They are significantly less likely to make a 'stupid decision,' because they intuitively grasp that this is a bad idea. And even in cases of mistakes of ignorance...a High Wisdom character is very likely to look at a situation and go "I don't know how to approach this. It's probably dangerous. It would be a bad idea to try without asking someone for advice."
A more likely example of a High Wisdom character making a major mistake could be because they noticed something, but didn't realize its significance at all. For example, they may notice the sigil-carved rock...but not realize that it's a trigger for a magical trap because they just don't know enough about Arcana to realize that's a thing you can do.
Your example of Tom to Tomm is not an example of a high wisdom character...because High Wisdom characters understand how people think, and would intuitively grasp that adding a letter to their name is NOT going to change how people perceive them.