Delve

According to wordpandit.com 

The word Delve is a verb. It means to carry out some search thoroughly or carefully. It is also used in a physical sense to signify digging, usually with a spade. All of us delve into our memories whenever we are trying to recall something important.

Its first known usage dates back to before 900. It has been derived from the Middle English word delven and the Old English word delfan.

delve  (dĕlv)
v. delved, delv·ing, delves
v.intr.
1. To search deeply and laboriously: delved through the court records.
2.
a. To research or make inquiries into something: scientists delving into gene regulation.
b. To undertake an activity or occupation undeterred by difficulty or uncertainty: delved into writing a blog.
c. To discuss or explain something, especially in detail: The article delves into the problems facing the banking system.
3. To enter or move into an area in which movement is difficult: The explorers delved into the forest.
4. To dig the ground, as with a spade.
v.tr.
Archaic To dig (ground) with a spade.
[Middle English delven, to dig, from Old English delfan.]
delv′er n.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.