The proof that the name is also FEMININE is by an Argentine film actress Teddie Gerard -- In which case it's a diminutive of THERESA/TERESA. https://en.wikipedia.org/wiki/Teddie_Gerard
This name can also be FEMININE as a diminutive of THEODORA or DOROTHEA, making it UNISEX. It was given to 30 girls in the USA in 1953 and recently, to 12 girls in 2016 and to 11 girls in 2018. https://www.names.org/n/Teddie/about [noted -ed]
https://en.wikipedia.org/wiki/Teddie_Gerard