• tamasā — by darkness
  Instrumental of tamas. Both the literal night and, in Gauḍīya extension, the tamoguṇa that obscures Bhagavān. The forest's darkness becomes a figure for saṁsāra — and only the guru's coming (v.39) lifts it.
• āvṛtāḥ — covered
  Past participle of ā-√vṛ. The directions themselves were covered — the disciples lost their compass. Gauḍīyas: when tamas covers, only Bhagavān/guru can reveal; the disciple's own effort cannot pierce it.
• nimnam — low
  Adjective: low-lying. The disciples could not distinguish hollows from heights. In Gauḍīya gloss: in saṁsāra, without guru-vidyā, one cannot tell the high from the low — values invert.
• kūlam — high land
  Bank, higher ground. Opposite of nimna. The pair nimna-kūla is the practical undifferentiation that defines disorientation.
• jala - mayam — with water all around
  Compound: jala (water) + maya (made of, full of). Everything was water. Gauḍīyas: the bhava-sāgara is right here — and in this verse it is literally the flooded forest the disciples wade.

When sun, land, and water all blur together, the disciples lose all coordinates — and yet they keep walking. Sevā does not wait for clarity; it continues into the dark. Gauḍīyas read the verse as a portrait of nirviśeṣa-affliction redeemed only by relationship.