It seems to be assumed (and I'll give an example in a second) that there is some connection between the 48 ways to acquire Torah (see the so-called sixth chapter of Avot) and the time of the year when we count the omer. What is the earliest source for this idea (or at least the earliest that you know of)? (48 being almost equal to 49 is not an acceptable answer.)
An example of the 'assumption' is this shiur being given at this time of the year. http://www.yutorah.org/lectures/lecture.cfm/876690/rabbi-dovid-gottlieb/48-kinyanei-torah-introduction/ Additionally, I have heard people discussing this in my local synagogues, but can't prove that to you...