The first Nepali word I recall learning in a natural language context (i.e. not from a grammar) is कण्डो (kaṇḍo), for which Turner:70 gives the following definition: "(vulgar) s. Buttock, bottom, rump, anus".
What has provided me with many moments of childish amusement is that this word is essentially homophonous with English condo, the truncated form of condominium: "(N. Amer.) An apartment house in which the units are owned individually, not by a company or co-operative; an apartment in such a building", OED. Thus overhearing people talking about selling their condos for $150,000 etc. always affords me a good (though usually silent) chortle.
Condominium is itself an interesting word, deriving ultimately from a modern Latin formation con+dominium, literally meaning "joint rulership" and appearing with that sense early on:
[a1714] BURNET Own Time (1823) IV. VI. 412 The duke of Holstein began to build some new forts..this, the Danes said, was contrary..to the condominium, which that king and the duke have in that duchy.
The use of condominium (and its truncation condo) to refer to an "individually-owned apartment" appears to be mainly a (recent) North American development; the earliest citation from the OED dates to 1962; the abbreviated condo appears soon after in 1964 (attributed to Chicagoans):
 Economist 31 Mar. 1255/1 The legal concept of buying a single flat, instead of a share in the whole building, is just making its way in the housing field in the United States where it is known as a ‘condominium’. Financial Times 27 Nov. 3/6 The condominium or the ‘condo’ as Chicagoans have come to know it is essentially a development from the co-operative concept.
The semantic development from "jointly ruled" to "individually-owned" is rather interesting, indicating that in modern usage the word must be have been reanalysed as monomorphemic (as the sense of "joint, together" of the prefix con-/com- is obviously no longer present).
Returning to the heart (or perhaps 'rump') of the matter, let us consider the etymology of Nepali kaṇḍo "buttock(s)". Turner notes that in Western dialects of Nepali it means "back, spine" and thus compares it to Sindhi kaṇḍo masc. "backbone", Lahndā kaṇḍ fem. "back", Hindi kā̃ṭā masc. "spine", Gujarati kā̃ṭo masc. "backbone", Marathi kā̃ṭā masc. "backbone". He notes if Nepali kaṇḍo is to be considered cognate with these words, it exhibits irregular phonetic development, for the expected form in Nepali would be *kā̃ṛo. He indicates this is not problematic given that "words denoting parts of the body often show irregular phonetic development, whether owing to deliberate deformation or borrowing from other dialects".
Turner suggests that, given this caveat, all of the above words could derive from Sanskrit kaṇṭa-, kaṇṭakáḥ "thorn, fish-bone", with later semantic widening/reanalysis to "bone, back-bone, bottom" etc. These Sanskrit forms are probably also the source, he notes, also of Romani kanro masc. "penis", Bengali kā̃ṭ "clitoris", and (with a much less naughty sense) Oriya kaṇṭi "the wooden part of a plough".
Given the apparent irregularities in the development of Nepali kaṇḍo, Turner also proposes a possible alternative etymology, from unattested Old Indo-Aryan *kāḍa-, citing modern forms: Romani kar m., Sindhi kāṛu masc., Gujarati kāḍ masc., all meaning "penis". This seems less likely to me, as the semantic development from "thorn, fish-bone" > "bone" > "backbone" (as in Western dialects of Nepali) and thence to "buttock(s)" in standard Nepali is much more natural than supposing that a word meaning "penis" developed to mean "backbone, spine" in Western Nepali. Plus, given the hypothetical ancestor *kāḍa, the nasal in Nepali kaṇḍo would be unexpected.
Development from "thorn" to "backbone" and thence to "buttocks" in standard Nepali is easily explicable. The tip of the backbone could be metaphorically conceptualised as a "thorn" (cf. the yogic concept of kuṇḍalinī "the corporeal energy residing in the base of the spine"). From "tip of the backbone" the sense could have been reinterpreted alternatively as "backbone, spine" in Western Nepali, and as "buttock(s)" in standard Nepali.
The other semantic developments in apparently cognate Romani kanro "penis" and Bengali kā̃ṭ "clitoris" represent alternate metaphorical extensions of the original sense "thorn". The naturalness of the metaphorical extension from "thorn" to "penis" is clear in the (nonce?) Hindi usage of कांटा (kāṇṭā) "thorn" in the song Kaanta Laga ("Pricked by a Thorn"):
Where the relevant line is बंगले के पीछे, तेरी बेरी के नीचे, हाय रे पिया, कांटा लगा ("behind the bungalow, beneath your jujube tree, oh darling, (I got) pricked by a thorn").