Wi-Fi certification for the alleged HTC Nexus tablet includes LMP in the firmware info, and multiple entries in the AOSP repository mention LMP.Before the last minute change to KitKat, Android 4.4 was planned to be called Key Lime Pie. Google even put a key lime pie icon in the easter egg for the system. Since Google couldn't have its pie last time around, it looks as though it is going for a slice with this update. Multiple items have surfaced which refer to the Android L update as "LMP". This can be found in the Android L preview SDK with a reference to "lmp-preview-release", the
So, at the very least, Google is using lemon meringue pie as an internal codename for the Android L release. That doesn't necessarily mean that the final update will carry that same nickname though. There is always a chance that Google pulls another marketing move with a major candy brand like Lemonheads, Lindor, or Laffy Taffy. For now, it looks like L will be Lemon Meringue Pie.
source: Android Police