Here is 3 ways of load an unexisting translation language into Odoo

First of all, this is for the scenario when  your language it's not in the lang list of Odoo

#first and long way but organized and able to be merged into core more easily

1- search all the used modules

2- copy their translation file en.po

that it's the english base translation that you could copy it from the source code for malayalam it is ml_In.po

if a module doesn't have an en.po file you could generate it

using the export translation and selecting english

3- rename the files to ml_IN.po, that is the correct iso code ml_IN

4- manually create a languaje for ml_IN using that iso code, you could name it like Malayalam India, but need to remains the iso code.

5- change the user to the new lang with everything translated in .po files

6- copy all the ml_IN.po to their respective odoo module folder, (for v7 and v8, not needed for v9, you also need to translate a .js called globalization for your lang you could find it at: openerp/addons/web/static/lib/datejs/globalization/en-US.js, after translate it to your lang put it in that same folder)

7- use syncronize terms

and I think that you will be ok

#second way, manually translate the terms: I think that is only for this database, I couldn't ensure that you could export those translated terms with an module structure, could be but I can't ensure it

1- manually create a languaje for ml_IN using that iso code, you could name it like Malayalam India, but need to remains the iso code.

2- change the user to the new lang with everything translated in .po files

3- use Syncronize Terms of that language and you will get a copy of the english terms for the malayalam language loaded into the database

4- using the menu Translated Terms and filtering by the terms by your language and you could use that view so you could edit the translation terms for Malayalam lang changing the translation values

#third way, portable to reuse it latter

1- just export all the modules translations that you are using into just one file and put it in a module so you will be translating just one .po and you could reinstall it latter more easily and feasible way

it's a hard work of translation that maybe you could contribute it to odoo so they could put it into core at least for the modules that you translate