Wagtail. An obsequious person; a harlot. I understand the analogy [dogs wag their tails; dogs are obedient], but I am not certain that I wholly agree with the latter part of this definition. Is a harlot a particularly obedient person? Doing what you’re told in exchange for money could be interpreted as ‘anyone who works’. If we are going to call a harlot a wagtail, we might as call everybody [with a job] a wagtail. I know, I know, it could simply have been a colloquialism, not a direct correlation with the initial definition. All the same.