lasergun

The story

1. Proto-Indo-European*lewk-
2. Proto-Indo-European*lewktom
3. Proto-Germanic*leuhtą
4. Proto-West Germanic*leuht
5. Old Englishlēoht
6. Middle Englishlight
7. Englishlight
8. Proto-Indo-European*h₃emh₃-
9. Proto-Indo-European*h₃emh₃-lo-s
10. Proto-Italic*amlos?
11. Proto-Indo-European*h₂ent-
12. Proto-Indo-European*h₂énts?
13. Proto-Indo-European*h₂m̥bʰí
14. Proto-Italic*amβi-
15. Latinambi-
16. Proto-Indo-European*pleh₁-
17. Proto-Indo-European*pl̥h₁nós
18. Proto-Italic*plēnos
19. Latinplēnus?
20. Latinambiplus?
21. Latinamplus
22. Proto-Indo-European*dʰeh₁-
23. Proto-Italic*θakos
24. Latinamplificō
25. Latinamplificātiō
26. Englishamplification
27. Proto-Indo-European*(s)tey-?
28. Latinstimulus
29. Latinstimulo
30. Latinstimulatus
31. Englishstimulate
32. Englishstimulated
33. Proto-Indo-European*h₁éǵʰ
34. Proto-Indo-European*h₁éǵʰs
35. Proto-Italic*eks
36. Latinex
37. Latinex-
38. Proto-Indo-European*mey-?
39. Proto-Indo-European*meyth₂-
40. Proto-Indo-European*méyth₂eti
41. Proto-Italic*meitō
42. Old Latinmītō
43. Latinmittō
44. Latinēmittō
45. Latinēmissiō
46. Middle Frenchémission
47. Englishemission
48. Latinradius
49. Latinradiō
50. Latinradiatio
51. Englishradiation
52. EnglishLASER
53. Englishlaser
54. Proto-Indo-European*gʷʰen-
55. Proto-Indo-European*gʷʰéntis
56. Proto-Germanic*gunþiz
57. Old Norsegunnr
58. Proto-Indo-European*kelh₂-
59. Proto-Indo-European*kelh₂tís
60. Proto-Germanic*hildiz
61. Old Norsehildr
62. Old NorseGunnhildr
63. Middle Englishgunne
64. Englishgun
65. English todaylasergun

From laser + gun.