Weight-lifters: weak verbs and strong verbs

I discovered that I am living three minutes away from the Brüder Grimm, the Grimm brothers who gave the world some of the most beautiful fairy-tales. They are six feet under at the cemetery in Schöneberg (picture), and I am living 60 feet above. So for me it is still a long way to go, but they are closer to us, the teachers and students of the German language, as we think. They not only collected and documented stories people told their children. They also contributed to the research of the German language and compiled one of the first German dictionaries. It was Jacob Grimm (1785 – 1863) who came up with the terms "weak verbs" and "strong verbs." You may have heard these terms and wondered if verbs are meant to be some sort of weight-lifters.
Strong verbs appear to us as irregular verbs. They change their vowel either when they are conjugated or when they are formed to preteritum (simple past) or to a participle.
Ich esse, du isst, er isst, wir essen, ihr esst. Preteritum: aßen. Participle: gegessen.
The verb trinken sounds like a regular guy.
Ich trinke, du trinkst, er trinkt etc. However, trinken changes in preteritum to tranken. Participle: getrunken.
Weak verbs are pretty regular, predictable individuals. They do not change their vowel. In preteritum they just stick a –t between verb stem and verb ending and as participle they are happy with a simple ge- as prefix.
Ich sage, du sagst, er sagt, wir sagen, ihr sagt. Preteritum: sagten. Participle: gesagt. So, why they are called weak and the others are called strong?
By mid of the 18^th century, German society – and with it the German language – underwent major changes. Jacob Grimm criticized the trend to standardize the conjugation of verbs as "language decay." The verbs that were not strong enough to withstand modernization were "weak" to him. The other verbs, the "strong" ones were untouched by time and fashion. We still speak and conjugate them, as peasants and noblemen did for centuries.
Jacob Grimm could not stem the tide. All new verbs that join the German vocabulary become weak verbs.
Ich e-maile, du googelst, wir surfen, er rappt, Sie shoppen, ihr skypt.