Let's start with the wart
It's not the kind you get on your knuckles or your knees; it's the one that invades the sole of the foot, the Plantar Wart. So that's logical: planta – on the sole of the foot.
These warts go by other names such as verrucas (From Latin verrūca) or myrmecias (From the Ancient Greek for ant). The origin of neither word is very useful, so plantar wart seems to be the best one to use.
Plantar warts are caused by a strain of the human papilloma virus (HPV) and occur on the sole or toes of the foot. Warts on the knuckles and knees are caused by other strains of HPV. The virus may enter through small cuts on the sole of the foot and then be forced to grow inwards by the routine pressure on the sole of the foot. They occur in about 10% of people who are genetically susceptible and can be very painful. Medical treatments may include freezing with liquid nitrogen or surgical removal. Some say they can be wished away.
What about the weed, Plantago?
You've probably seen them with their long radiating leaves growing flat to the ground and that's where they get their name: like the soles of a foot (remember, planta means sole of the foot).
There are about 260 species world wide, especially in temperate regions. Australia has 24 endemic and 8 introduced species, some of which are invasive weeds. Interestingly, Plantago hedleyi Maiden is endemic to Lord Howe Island. Worth a visit just to see this rarity.
Surprisingly too, plants in the Plantago genus provide edible components (psyllium husks) and a variety of herbal medicines.
So far so good: all related to the sole of the foot.
And what about the banana?
Well it's not the one you see in your fruit bowl, but one that is hardly sweet called a plantain (on the right in the picture). Where's the link to planta?
There isn't one. It would seem that this name probably comes from the Caribbean palatana for banana.
Plantains are grown in many (100+) countries in the tropics and they are often a major staple food there. A hectare of land can yield as much as three and a half tonnes of plantains. They are low in sodium, high in potassium and vitamins A and C. About 300 grams of cooked plantains deliver only 125 calories (about 500 kilojoules).
But don't feel complacent because the word plant (and a plantain is a plant after all) probably comes from the Latin plantare - to drive in with the feet; push into the ground with the sole of the foot.
So we have come full circle because the sole of the foot is the planta.