J.E. Sandys, A History of Classical Scholarship Vol. 1:
The Alexandrian use of γραμματικός in the above sense was apparently somewhat later than the use of κριτικός in the same general sense. The word κριτικός is found in a pseudo-platonic dialogue of uncertain date, in a passage in which the Greek boy, on reaching the age of seven, is humorously described as ‘suffering much at the hands of tutors and trainers, and teachers of reading and writing’ (γραμματισταί), and as ‘passing, as he grows up, under the control of teachers of mathematics, tactics and criticism’ (κριτικοί). There is reason to believe that, just as this use of κριτικοί probably preceded that of γραμματικοί in its Alexandrian sense, similarly the term κριτική was earlier than the corresponding term γραμματική.
Criticism was regarded as founded by Aristotle, and among its foremost representatives in the Alexandrian and Pergamene age were Aristarchus at Alexandria and Crates at Pergamon. Crates and his pupils of the Pergamene School subordinated γραμματική to κριτική, and preferred to be called κριτικοί. Criticism was among the higher functions of the γραμματικός. Thus Athenaeus (fl. c. 200 A.D.) describes the authorship of certain poems as a matter for the critical judgement (κρίνειν) of the best γραμματικοί; and Galen (130-200 a.d.) wrote a treatise on the question whether any one could be κριτικός and also γραμματικός, implying a certain distinction between these terms.
Meanwhile, more than two centuries before Galen, Cicero in one of his letters, after alluding to Aristarchus, describes himself as about to decide, tamquam criticus antiquus, whether a certain document is genuine or spurious. The term is also used by Horace, in a passage in which he calls Ennius an alter Homerus, ut critici dicunt, where Varro is probably meant. It also occurs repeatedly in the Commentary on Virgil by Servius, in the frequent phrase notant critici. Lastly, κριτικός is found as a designation of Dionysius of Halicarnassus; also of Munatius of Tralles (the tutor of Herodes Atticus) in the second century, and of Cassius Longinus in the third. Thus it appears that, owing to a certain ambiguity in the term γραμματικός with its lower sense of ‘grammarian’ and its higher sense of ‘scholar’, and a corresponding ambiguity in the term γραμματική with its lower sense of ‘grammar’ and its higher sense of ‘scholarly criticism’, the term κριτικός was generally applied to those of the γραμματικοί who excelled in the higher branch of γραμματική, that of literary criticism. We may conclude on the whole that one who in modern times is in English called a ‘scholar’, in French a philologue, and in German a philolog, would in ancient times have been called either a grammaticus or a criticus, according to his degree of distinction, the latter being the higher term of the two; while the term philologus in general designated a lover of learning, or a learned student of varied accomplishments and especially of antiquarian tastes.
 Axiochus 366 E. Cp. P Girard, L’éducation athénienne, p. 224 – 7
 Schol. on Dionysius Thrax, p. 673, 19 ἐπιγέγραπται γὰρ τὸ παρὸν σύγγραμα κατὰ μέν τινας περὶ γραμματκικῆς κατὰ δέ ἑτέρους περὶ κριτικῆς τέχνης. κριτικὴ δὲ λέγεται ἡ τέχνη ἐκ τοῦ καλλίστου μέρους. Bekker, Anecdota, p.1140 κριτικὴ δὲ λέγεται ἡ τέχνη ἐκ τοῦ καλλίστου μέρους. τὸ πρότερον κριτικὴ ἐλέγετο (ἡ γραμματική), καὶ οἱ ταύτην μετιόντες κριτικοί. Cp. Usener in Susemihl l.c. ii 665
 Dion Chrysostom, Or. 53, 1, ᾿Αρίσταρχος καὶ Κράτης καὶ ἕτεροι πλείους τῶν ὕστερον γραμματικῶν κληθέντων, πρότερον δὲ κριτικῶν. καὶ δὴ καὶ αὐτὸς ᾿Αριστοτέλης, ἀφ’ οὗ φασι τὴν κριτικήν τε καὶ γραμματικὴν ἀρχὴν λαβεῖν.
 Sextus Emp., Math. i 79, (Κράτης) ἐκεῖνος ἔλεγε διαφέρειν τὸν κριτικὸν τοῦ γραμματικοῦ, καὶ τὸν μὲν κριτικὸν πάσης, φησί, δεῖ λογικῆς ἐπιστήμης ἔμπειρον εἶναι, τὸν δὲ γραμματικὸν ἁπλῶς γλωσσῶν ἐξηγητικὸν καὶ προσῳδίας ἀποδοτικὸν κτλ., and 248, γραμματικῆς, συμφανές. Ταυρίσκος γοῦν ὁ Κράτητος ἀκουστής, ὥσπερ οἱ ἄλλοι κριτικοὶ ὑποτάσσων τῇ κριτικῇ τὴν γραμματικήν κτλ.
 p. 116
 ad Fam. Ix 10, I.
 Ep. II i 51.
 Servius on Aen. i 71, viii 731, xi 188 etc. (ap. Lehrs l.c., p.397 note)
 Usener on Dionysius Hal. De Imitatione p. 133 note; and Lehrs l.c. p. 395.
 Lehrs l.c. p. 379