avanasavanakarmaNyAtmalokasya ra~NgI
	bhuvanaguruvara tvAm kalpayitvA samartham |
tadanu bhujagarAjottu~Nga parya~NkashAyI
	rachayati sukhanidrAm raghavANAm kulendra: ||

Meaning:

bhuvanaguruvara 		- O! LOkacharya.
ra~NgI 				- Sri Ranganatha 
raghavANAm kula indra: 		- who is the family deity for the Raghu lineage of kings
samartham 			- being competent
avana savana karmaNi 		- in the big act of saving the
Atma lokasya 			- multitude of jIvas
tvAm kalpayitvA 		- conceived of you;
tadanu 				- after that
rachayati 			- He does
sukha nidrAm 			- the act of resting comfortably (without thought)
bhujagarAja uttu~Nga 
  parya~Nka shAyI 		- on the lofty bed of Adisesha.

Vyakhyana Saram:
Sriman Narayana gave the chetanas their bodies and senses so that they can surrender to Him and attain His divine abode. Through the rishis, He gave the Sastras so that they can gain the appropriate knowledge. Throuh Nara, Periya Pirattiyar and Arjuna, He gave the Rahasy Trayam. He also descended as various avataras and through instruction and performance explained the same. As this did not bear fruit, He brought forth the Azhvars - to have chetanas follow other chetanas like themselves and reach Him. That did not work either. Azhvars sang pasurams about Him, but did not explain all the meanings of those pasurams to the common people. To explain those meanings and additional meanings, He sent forth the acharyas starting with Nathamunigal.

The early acharyas spoke mostly in the Sanskrit language. Ramanuja wrote his works in Sanskrit as well, but he also instructed his disciples and their disciples to explain all the critical meanings of the sampradhayam to everyone who is interested in the easily understood (at that time) language of maNi pravALam (a mixture of Sanskrit and Tamil).

Pillai Lokacharyar wrote the ashtadasa rahasyas - 18 granthas in maNi pravaLam explaining these wonderful meanings, such that many people were able to understand and follow them and attain liberation.

Desikan is stating in this shloka that because of this, Sri Ranganatha's work is being taken care of and He is able to rest comfortably on His bed of Adisesha.