1) Cry of encouragement 2) Cry to a good dog 3) Encouragement to a little lad 4) Encouraging cry 5) Encouraging phrase 6) Encouraging utterance 7) Encouraging word 8) Exclusively Anglo word 9) Exclusively Saxon word 10) Male chauvinist cheer 11) Parental words of praise 12) Slangy expression of approval 
Attaboy is a slang expression of approval or exhortation.
(used as an enthusiastic expression of encouragement or approval to a boy, man, or male animal.)