"header" - key terms from Wikipedia

authentication header
bmp header
custom header
dib header
extension header
file header
fixed header
gpt header
grille header	bar
header
header	and data
header	block
header	constant
header	errors
header	field
header	fields
header	file
header	files
header	include
header	length
header	names
header	panel
header	table
http header
icmp header
ip header
llc header
mail header
message header
mpls header
next extension header
next header
ogg page header
packet header
partition table header
program header
referer header
rtp header
section header
snap header
tcp header
udp header
volume header