as the name Alma came into prominence in 1854/5 with the Crimean war - it is likely to date from about that period (tho might be a rebuild of an earlier cottage) - in 1881 directory for Bride - Christian, William, farmer, Alma Cottage (in 1889 the more helpful - Christian William Henry, farmer, Alma cottage)
There is a leaflet on tracing property in Manx Museum - the deeds for this period are likely to go online soon at iMuseum but before this the staff can guide you through the process.