This ramble arises after flipping through the (then, 1978) Recent Developments in Historical Phonology. While any data is better than no data, an un-Greeked, or un-LSJed reader might not be able to rate the relative values of Greek lexical data presented in LSJ. In that case, the data set for comparative linguistics can become something of a pot-luck. Take this for example,
At face-value, those words have seemingly equal attestation or support, but actually? From 5 years study of (and relatively little progress in) Latvian, I know that we can expect that every 3 - 5 year old Latvian speaking child comprehends and uses slapjš. It is core childhood vocabulary word generally describing the state of things affected by water. Perhaps the meaning is narrower in Lithuanian or perhaps not, but I myself wouldn’t trust what I might say about it. κλέπας is given in LSJ, in what I assume is a verbatim quote from Hysechius:
κλέπας: νοτερόν, πηλῶδες: ἢ δασύ, ἢ ὑγρόν, Hsch.
While one might be tempted to ammend δασύ to a form of δροσόεις when the apparent mis-match in the ‘wet’ set is noticed, another (perhaps more preferable) solution is possible too. The LSJ entry for δασύς contains reference to a later writer:
i.e.
The main idea of the passage is that rain from moist clouds makes a difference. Presumably, the type of clouds described by DS are nimbostratus clouds - with their prolonged periods of rain.
Not mentioned in the LSJ entry for δασύς, but suggested by association in the word list given by Hysechus for κλέπας, and plausible in Diodorus Siculus, the meaning ‘wet’ in a broad range of senses is similar to the range of meanings that the Latvian slapjš is the meaning ‘wet’.
We usually think of Hesychus as the authour of lists of obscure words, but here is a word with quite a range of meanings; νοτερόν (the wet or moist whatever that is itself, but now the wet version), πηλῶδες the muddy (ground, path or field): ἢ δασύ (the water-ladden clouds - if my analysis of the DS passage is sound), ἢ ὑγρόν (the moist whatever that changed from solid or gaseous to “liquid” by the addition of water). Rain-bearing clouds are typically not as translucent (sunshine blocked) as non rain-bearing clouds, because are they are “thick”, and that “thickness” comes about they are laden with (condensed) rainwater ready to fall.
If we do not explain away κλέπας (with its neuter adjectival ending -ας) as the record in Greek script - using kappa to represent a palatalised silibant - of an exotic word akin to Lithuanian šlapias, brought by a wandering (or enslaved) Balt, then we are left with the problem of explaining an “obscure” Greek word, with a very broad range of meanings. I think Hesychius or one of his predecessors may have had to have seen it in at least 3 or 4 different contexts to make that entry.