The main clues to what the word ‘æstel’ means are:
1. Ælfric of Eynsham’s Glossary, where ‘æstel’ is glossed as indicatorium
2. A ms. of Alfred’s translation of the Regula pastoralis where Alfred’s use of the word ‘æstel’ in his own prologue is glossed as indicatorium and festuca.
To dispose of no 2. : the glossator is identified as the ‘Tremulous Hand of Worcester’, a 13th-c. scribe, probably based in Worcester, who glossed a number of Old English manuscripts. Since he was working at least 300 years after Alfred’s time, and well after the Norman Conquest, he would not have had first hand knowledge of Old English. He may, in all probability, have consulted a manuscript of Ælfric’s Glossary to find out what this unusual word meant. In that case, his can only be considered secondary evidence.
Therefore, looking at Ælfric’s Glossary:
Ælfric of Eynsham, or Ælfric the Grammarian, was working in the late 10th. c, much closer to Alfred’s time – and an ‘Anglo-Saxon’. He wrote a Grammar and Glossary, supposedly to help students learn Latin. The supposition would then, surely, be that they understood the Old English words given and were to learn the Latin equivalent.
On this, more anon …