Schebeck speculates that Wurrulul (N132) is a 'ceremonial name (?)' of the Rirradjingu N140; wurrulul means 'blow fly' (2001:96).
Oates says it is a 'Riraidjangu-speaking group now extinct' (1975:315, 387).
The Yolngu Matha Dictionary records 'wurulul ~ wurrulul : fly, bush fly'. For Yolngu languages see Yolngu Matha N230.
Speaker numbers were measured differently across the censuses and various other sources listed in AUSTLANG. You are encouraged to refer to the sources.
Speaker numbers for ‘NILS 2004’ and ‘2005 estimate’ come from 'Table F.3: Numbers of speakers of Australian Indigenous languages (various surveys)' in 'Appendix F NILS endangerment and absolute number results' in McConvell, Marmion and McNicol 2005, pages 198-230 (PDF, 2.5MB).