The affix cha comes, also, only in the sense of 'like this' after a compound noun which contains in itself the force of 'like this'.,
The word तद् refers to इव, and तद्विषय means इवार्थविषय ॥ A compound which is formed with the force of इव, takes the affix छ, when a second इव is to be indicated. In the chapter on Compounds, no samasa is taught with the force of इव; this sutra, therefore, indicates by implication that such a samasa of two nouns can be formed, having hidden in it the sense of इव ॥ Such a samasa will come under the head of सुप् सुपा समासः 2.1.4.
Thus काकतालीयम्, अजाकृपाणीयम्, अन्धकवर्त्तिकीयम् ॥
The word काकतालीय means 'like the crow and the palm-fruit': 'the unexpected and sudden fall of a plam-fruit upon the head of a crow so as to kill it, at the very moment of its sitting on a branch of that tree; and is used to denote a very unexpected and accidental occurence'. Thus Devadatta happens to enter a village, and on that very day, robbers happen to attack the village, and in the fray, Devadatta is killed, this coincidence of the robbers and Devadatta is called काकतालीयसमागमः, and the killing of Devadatta is like that of the crow by the ताल fruit. The first case of समागमः will form the compound, the second case of वधः will give rise to the affixing of छ, as काकतालीयो देवदत्तस्य वधः (the compound काकताल meaning काकतालसमागमसदृशश्चोर समागमः) and the derivative word काकतालीय meaning काकमरणसदृशः) :
Similarly अजाकृपाणीय means \like the death of a goat (aja) by the accidental falling of a sword (kripana) as the goat was passing\. Similarly अन्धकवर्त्तकीय means \like the accidental falling of a vulture (vartika) in to the hands of a blind person who thus captures it\. All these are unintentional (atarkita) and curious (chitrikarana) coincidences. In short, these words mean 'accidentally', 'unexpectedly'.,