Backwards and Upside-Down

Sometimes, the L2 speaker will use a wrong word or phrase, just because there is a gap in their lexical knowledge. For example, I was playing catch with Moshe, age 8, and he asked me to “throw the ball from the bottom.” He simply was not familiar with the term “throw it underhand,” so he used “from the bottom,” which is a word-for-word translation of מלמטה. There are other times, however, when they do know the correct word, but they say the wrong one, probably due to L1 interference. The very same Moshe, upon seeing that his little brother’s pajama shirt was on backwards, said: “Your shirt is upside-down.”  He has used the word “backwards” many times. What seems to have happened here is that the Hebrew word הפוך can be used either for backwards or upside-down, and he just crossed up which one to use.
Addendum: Believe it or not, just two days later, Chana (age 10) made the exact same mistake of using "upside-down" instead of "backwards" for my son's shirt (yes, when he dresses himself, he often puts his shirt on upside-down, I mean backwards).