How to convert species names into common names?
use the NCBI taxon dump under ftp://ftp.ncbi.nih.gov/pub/taxonomy

in taxdmp.zip you'll find all the names for a given NCBI taxon

$ grep -w ^9606 names.dmp 
9606    |   Homo sapiens    |       |   scientific name |
9606    |   Homo sapiens Linnaeus, 1758 |       |   authority   |
9606    |   human   |       |   genbank common name |
9606    |   man |       |   common name |