By M. A. Alwar
Indhanam is a neutral form.
It is derived from "indhe dīpyate agniranena" which means 'Fire burns by this'.
Grammatically, it can be split as indha+lyuṭ which denotes the instrumental sense. It it the fuel used for lighting fire like grass, firewood, etc.
The synonyms are:
“The headman of the village should collect food, water, fuel, etc. which is to be given to the king daily, by the villagers”. 
- As per Amara
- As per Śabdaratnāvalī.
- जालानी काठ in Hindi.
- Manu 7|118
- Shabdakalpadrumah by Raja Radhakantdev, Varadaprasada Vasu, Haricarana Vasu