From Polyglot Club WIKI
While there is a very slight "nuance" of different meaning, the two expressions still carry (roughly) the same meaning.
There is a nuance of difference between "Although" and "Even though" expressions in certain, but very few, instances...
Allow me to illustrate w/ an example:
Example 1: Same meaning
- a) Although she did not want to, Sarah went to the dance.
- b) Even though she did not want to, Sarah went to the dance.
Example 2: Slightly different meaning(s)
- a) Although it was a cool day, I went swimming.
- b) I went swiming even though it was a cool day.