Of the sea
Merrissa is a modern elaboration of Marissa, which is derived from the Latin 'maris' meaning 'of the sea'. It is often associated with the name Mary or the title Stella Maris, meaning 'Star of the Sea'. This specific spelling is rare and adds a rhythmic, multi-syllabic quality to the name.
Less common today
Merrissa isn't in the latest US Top 1000. It last peaked at #6,395 in 1990.
US births per 5-year period, 1990βpresent (SSA data).