It is not an acronym as popularly believed.
1	It	it	PRON	PRP	Case=Nom|Gender=Neut|Number=Sing|Person=3|PronType=Prs	5	nsubj	5:nsubj	_
2	is	be	AUX	VBZ	Mood=Ind|Number=Sing|Person=3|Tense=Pres|VerbForm=Fin	5	cop	5:cop	_
3	not	not	PART	RB	_	5	advmod	5:advmod	_
4	an	a	DET	DT	Definite=Ind|PronType=Art	5	det	5:det	_
5	acronym	acronym	NOUN	NN	Number=Sing	0	root	0:root	_
6	as	as	SCONJ	IN	_	8	mark	8:mark	_
7	popularly	popularly	ADV	RB	_	8	advmod	8:advmod	_
8	believed	believe	VERB	VBN	Tense=Past|VerbForm=Part	5	advcl	5:advcl:as	SpaceAfter=No
9	.	.	PUNCT	.	_	5	punct	5:punct	_
