I have discussed about the entry of sea fishermen to South India. I wasn't able to place them to any linguistic group clearly. But it appears a section of them could have had IE linguistic origins from north-western India(or Pakistan).
The Old Sindhi word for fisherman was 'mahavar'. If you observe, few Tamils still make h->g sound changes (mahEza becomes magEza); It is possible that in remote past old Tuluvas might have made the similar sound changes.
Hence, the initial change is mahavar->magavar.
Another vowel replacement common to Tulu/Malayalam is 'av' to a long vowel. eg. avan->On(=he) in Kasaragod Malayalam. aval->Al(=she) in Tulu.
Now, the second change magavar -> magAr
Even today, there is a fishermen community called Mohanna residing in Sindh. Recently, genetic studies have been conducted on them. I don't have access to the article. But I found the study at an Egyptian forum.
From the study:
The Mohanna have been included in such a
study for the very first time. This ethnic group resides in the
Sindh province, and their livelihood is fishing; in fact, the word
Mohanna in Sindhi means fishermen. Not much is known
about this population, but it is believed that the Mohanna were
the original inhabitants of the subcontinent, who were then
replaced by the Aryans when they invaded this area. However,
little pockets of this ethnic group were left over after the
Aryan invasion. In Pakistan this pocket exists in the south
around the river Indus, where the Mohanna presently reside.
I don't give much importance to autosomal analysis. I believe only neutral haplogroup markers have any legitamacy in migration history.
Anyway, one thing we can observe here that Old Sindhi maha* has turned into moha* in present day Sindhi. Therefore, it is possible that mahavar might have arrived as mohavar to Tulu region.
Hence, m(a/o)havar ->mogavar->mogAr ->mogEr
It is possible that Mohanna might have had pre-IE origins. However, as their name suggests a section of them migrated after IE-isation of their community.
It would be interesting to see if present day Mogera-s of Tulu regions have any Y-Haplogroups that matches to Mohanna of Pakistan.