This is a people name, Oates and Oates define Walmbarddha as a group of different peoples including Lama-lama Y136, Gan-ganda Y138 and Wurangung Y66, that is, various peoples from Princess Charlotte Bay (1970:209). However, Oates later indicates this is a mis-identification (1975:385).
Sutton says that Oates and Oates' Walmbarrdha group is probably based on a Gugu Yimidhirr phrase Bama Walmbaarrga, a cover term for peoples of Princess Charlotte Bay (1993:34).
Previously, the code Y147 was listed in Pathways Thesaurus authorities: Lamalama / Bakanambia language (Y58,Y136,Y140, Y147) (Qld SD54-12) and Lamalama / Bakanambia language (Y58, Y136, Y140, Y147) (Qld SD54-12).
Hale and Tindale say that Kokolamalama Y136 who live around the Normanby and North Kennedy Rivers and Jane Table Hill [sic] call themselves Bakanambia (and Wanbara) (1933:68). Following them, Capell lists Bajganambia with alternate names Wambara and (koko) Lamalama Y136 (1963 code Y18).
'Walmbarddha' has the same referents as 'Walmbaria', which was previously listed in the Thesaurus as Walmbaria/Gambilmugu language and people; see Y61 for a full description.
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).