I pulled these definitions from the Merriam-Webster site because I wasn't completely sure what "Deathly Hallows" really were.

deathly (definition)

Main Entry: death·ly
Function: adjective
1 : FATAL
2 : of, relating to, or suggestive of death
Text: likely to cause or capable of causing death


hallow (definition)

Main Entry: hal·low
Function: transitive verb
Etymology: Middle English halowen, from Old English hAlgian, from hAlig holy
1 : to make holy or set apart for holy use
2 : to respect greatly : VENERATE
Text: to make holy through prayers or ritual


So...likely to cause or capable of causing death...and...to make holy through prayers or ritual.

My interpretation...we already knew this...Harry "causes death" to each piece of Voldemort's soul by casting spells (through ritual) therefore making the world less evil (more holy).

Harry destroys Horcruxes. Harry destroys Voldemort. Stuff happens. Characters die. The End.