B737-800 First Officer reported a tail strike warning had illuminated on the Captain's HUD upon landing but after walking around the aircraft; no evidence was found of a tail strike.

Narrative

While on the ILS approach to Runway XX in ZZZ; the aircraft touched down in the touchdown zone and by my account was a normal landing. After reflecting on the landing further; I did flare a slight amount more than usual. However; I thought nothing of it. The aircraft decelerated normally and we exited the runway to the left on Taxiway 1. At 60 kt. the Captain took control of the aircraft and we proceeded to the gate without incident. Upon completion of the shutdown checklist; the Captain informed me that TAILSTRIKE" had illuminated in the Head-up Display (HUD) upon touchdown. I immediately went outside to the ramp to investigate as to whether a tail strike had actually occurred or not. After investigation; there was no evidence of a tail strike. Upon returning to the flight deck; the Captain and I decided to make a phone call to the pilot representative; Person A. Person A advised us to write the aircraft up in the logbook for "tail strike displayed in the Captain's HUD upon landing." Maintenance subsequently investigated the write-up and determined that the aircraft did not have any evidence of a tail strike. The aircraft was returned to service and it continued on its scheduled flight to ZZZ1.After further discussion with Person A and other representatives from several committees; it was suggested that the Captain and I file a safety report to compile further evidence for when this situation happens in the future with other flight crews; and that possible manual updates and guidance could be coming forth for the entire pilot group on the 737 fleet.Cause: My rate of rotation in my landing flare triggered the HUD system to display the caution message "TAILSTRIKE" to the Captain. Going forward I will most assuredly have a more gradual rate of nose up pitch to establish an adequate landing flare.Because neither of us had seen this message in real life or in the simulator before; we were absolutely astonished and were both thinking "could it be possible we had a tail strike?" It was quite alarming and scary until the moment I walked around the aircraft to see that no damage had been done to the fuselage.I agree with the idea of filing this report to make it known that if you are unprepared for the message to be displayed in the HUD and that if you do not know what it means; it can add an unnecessary level of stress to what amounted to be a benign situation in this case. I understand the reason for the HUD system to display this cautionary message and that it is monitoring the rate of rotation at which you are flaring the aircraft.In hindsight; the best decision we could have made at the time given the information we had was to make a logbook entry; notify the company; and notify our representative as to what had occurred. I did not feel right walking away from the aircraft without Maintenance Control putting eyes on the aircraft and giving the all clear - that we did not have a tail strike."